Showing papers on "Solar power published in 2017"

Copper indium gallium selenide based solar cells – a review

Abstract: Copper indium gallium selenide (CIGS) based solar cells are receiving worldwide attention for solar power generation. They are efficient thin film solar cells that have achieved 22.8% efficiency comparable to crystalline silicon (c-Si) wafer based solar cells. For a production capacity of 1000 MW y−1 with 15% module efficiency, the CIGS module production cost is expected to be $0.34 W−1. For CIGS cells over glass, a graded bandgap high temperature deposition process has been established, however, this process has not been established for CIGS over flexible polymer substrates which is a low temperature process. For small area devices, the main focus is precise control over CIGS film stoichiometry and efficiency. For industrial production, apart from stoichiometry and efficiency, low-cost, reproducibility, high-throughput and process tolerance are of much importance in commercializing the technology. Due to process complexity, CIGS module production is lagging behind that of cadmium telluride (CdTe) modules. In this review article, the working mechanism of CIGS solar cells with a back surface field, the importance of developing CIGS solar cells, and the limitations for their commercialization are discussed. CIGS solar cells are compared with c-Si solar cells. After briefly reviewing the history of the chalcopyrite alloy system, graded bandgaps, effects of sodium distribution in CIGS layers, growth of CIGS layers using various techniques, role of buffer layer/transparent conducting oxides, CdS free buffer layers, concerns related to flexible solar cells, and factors affecting the cell efficiency are reviewed. Further efficiency improvement options are discussed. Cell stability, challenges, solutions and future prospects of CIGS solar cells are outlined.

Review of commercial thermal energy storage in concentrated solar power plants: Steam vs. molten salts

Abstract: Thermal energy storage systems are key components of concentrating solar power plants in order to offer energy dispatchability to adapt the electricity power production to the curve demand. This paper presents a review of the current commercial thermal energy storage systems used in solar thermal power plants: steam accumulators and molten salts. It describes the mentioned storage concepts and the results of their economic evaluation. The economic value of the TES system is assessed by the Levelized Cost of Electricity (LCOE) calculation, an economic performance metric commonly used in power generation in order to compare cost of electricity among different power generation sources. Lots of studies have been done in the past to compare the LCOE of a complete solar thermal power plant using thermal energy storage systems. However, no specific studies related to the thermal energy storage levelized cost of electricity itself were done. The objective of this study is focused in the comparison of the TES LCOE where calculations are done for a 100 MW Rankine cycle with different plant configuration and for different storage sizes ranging from 1 to 9 h of equivalent full capacity operation.

Understanding future emissions from low-carbon power systems by integration of life-cycle assessment and integrated energy modelling

Abstract: Both fossil-fuel and non-fossil-fuel power technologies induce life-cycle greenhouse gas emissions, mainly due to their embodied energy requirements for construction and operation, and upstream CH4 emissions. Here, we integrate prospective life-cycle assessment with global integrated energy–economy–land-use–climate modelling to explore life-cycle emissions of future low-carbon power supply systems and implications for technology choice. Future per-unit life-cycle emissions differ substantially across technologies. For a climate protection scenario, we project life-cycle emissions from fossil fuel carbon capture and sequestration plants of 78–110 gCO2eq kWh−1, compared with 3.5–12 gCO2eq kWh−1 for nuclear, wind and solar power for 2050. Life-cycle emissions from hydropower and bioenergy are substantial (∼100 gCO2eq kWh−1), but highly uncertain. We find that cumulative emissions attributable to upscaling low-carbon power other than hydropower are small compared with direct sectoral fossil fuel emissions and the total carbon budget. Fully considering life-cycle greenhouse gas emissions has only modest effects on the scale and structure of power production in cost-optimal mitigation scenarios. All energy generation technologies emit greenhouse gases during their life cycle as a result of construction and operation. Pehl et al. integrate life-cycle assessment and energy modelling to analyse the emissions contributions of different technologies across their lifespan in future low-carbon power systems.

Evaluation of a proposal for reliable low-cost grid power with 100% wind, water, and solar

Abstract: A number of analyses, meta-analyses, and assessments, including those performed by the Intergovernmental Panel on Climate Change, the National Oceanic and Atmospheric Administration, the National Renewable Energy Laboratory, and the International Energy Agency, have concluded that deployment of a diverse portfolio of clean energy technologies makes a transition to a low-carbon-emission energy system both more feasible and less costly than other pathways. In contrast, Jacobson et al. [Jacobson MZ, Delucchi MA, Cameron MA, Frew BA (2015) Proc Natl Acad Sci USA 112(49):15060-15065] argue that it is feasible to provide "low-cost solutions to the grid reliability problem with 100% penetration of WWS [wind, water and solar power] across all energy sectors in the continental United States between 2050 and 2055", with only electricity and hydrogen as energy carriers. In this paper, we evaluate that study and find significant shortcomings in the analysis. In particular, we point out that this work used invalid modeling tools, contained modeling errors, and made implausible and inadequately supported assumptions. Policy makers should treat with caution any visions of a rapid, reliable, and low-cost transition to entire energy systems that relies almost exclusively on wind, solar, and hydroelectric power.

Balancing Europe’s wind-power output through spatial deployment informed by weather regimes

Abstract: Weather regimes drive variability in wind-power generation across Europe, affecting energy security. Strategically deployed wind turbines in regions of contrasting weather regime behaviour can be used to balance wind capacity and minimize output variability. As wind and solar power provide a growing share of Europe’s electricity1, understanding and accommodating their variability on multiple timescales remains a critical problem. On weekly timescales, variability is related to long-lasting weather conditions, called weather regimes2,3,4,5, which can cause lulls with a loss of wind power across neighbouring countries6. Here we show that weather regimes provide a meteorological explanation for multi-day fluctuations in Europe’s wind power and can help guide new deployment pathways that minimize this variability. Mean generation during different regimes currently ranges from 22 GW to 44 GW and is expected to triple by 2030 with current planning strategies. However, balancing future wind capacity across regions with contrasting inter-regime behaviour—specifically deploying in the Balkans instead of the North Sea—would almost eliminate these output variations, maintain mean generation, and increase fleet-wide minimum output. Solar photovoltaics could balance low-wind regimes locally, but only by expanding current capacity tenfold. New deployment strategies based on an understanding of continent-scale wind patterns and pan-European collaboration could enable a high share of wind energy whilst minimizing the negative impacts of output variability.

Investigation of feasibility study of solar farms deployment using hybrid AHP-TOPSIS analysis: Case study of India

Abstract: Presently, the usage of solar energy has increased with the advent of Renewable Energy Sources (RES) and bypassing traditional energy sources such as fossil fuels. Government of India (GoI) is adopting various policy measures to promote diffusion of solar energy across the nation and has huge solar energy investment plans in near future. In this regard, selection of appropriate site for solar power installation is of prime concern. It is a critical issue that needs to be analyzed in depth for producing solar power efficiently because various key factors viz. social, technical, economic, environmental and political aspects are associated with it. Considering the fact that there are lots of factors which affect the solar farm site selection, it is imperative to organize them in a systematic hierarchy. In this direction, present study aims to select appropriate site in an Indian case using hybrid combination of two Multi Criteria Evaluation (MCE) methods- Analytical Hierarchical Process (AHP) and fuzzy Technique for Order Preference by Similarity to Ideal Solution (TOPSIS). Present investigation reveals that Sonepat is the best location for solar installation followed by Rohtak, Chandigarh, Gurgaon and Hisar in state of Haryana, India. The purpose of the investigation is to present an effective, efficient and systematic decision support framework which might help policy planners in the evaluation process of appropriate solar farm site selection in India.

Predicting and optimising the energy yield of perovskite-on-silicon tandem solar cells under real world conditions

Abstract: Metal halide perovskite absorber materials have emerged as a potential new technology for large-scale low-cost photovoltaic solar power. One great advantage lies in the ability to tune their light absorption band across the visible to near infrared spectral regions, making it an ideal candidate for tandem solar cell applications, in combination with traditional crystalline silicon. For a multi-junction solar cell to operate at peak efficiency, the current generation in all junctions must closely match, especially for monolithically integrated tandem architectures. It is feasible to achieve such matching under a standardized solar spectrum with direct illumination. However, under real world conditions the spectrum of sun light, and the fraction of diffuse to direct sun light varies considerably depending upon the location and weather conditions. Hence, it is not directly obvious how much more efficient a multi-junction solar cell needs to be, in comparison to a single junction cell, before it will produce more electrical power under real world conditions. Here, we introduce a rigorous optical and device simulation to optimize perovskite-on-silicon tandem solar cells and identify feasibility of various optimisation parameters to achieve the highest possible efficiencies. Firstly, we determine that the ideal bandgap for a perovskite “top-cell” is 1.65 eV, which will deliver up to 32% efficiency when combined with a silicon rear cell. Furthermore, we calculate the annual energy yield under hourly spectrum changes at different locations and optimize the stack to show that tandem solar cells are yielding up to 30% more energy output than the single junction silicon. Most critically, the standardized air mass 1.5 efficiency measurement improvements observed for the tandems cells, translate almost entirely to the same fractional improvement in energy yield. Hence, the efficiency of the tandem cell is not significantly “de-rated” by real world spectral variations. We do observe however, that tandem solar cell stacks can deliver further improvements by optimising differently depending on the location of installation. Our results justify the drive towards monolithically integrated multi-junction solar cells, and will enable guidance to design the ideal perovskite tandem device and allow estimations for energy yield and hence the levelized cost of electricity.

Space-time variability of climate variables and intermittent renewable electricity production – A review

Abstract: A major part of renewable electricity production is characterized by a large degree of intermittency driven by the natural variability of climate factors such as air temperature, wind velocity, solar radiation, precipitation, evaporation, and river runoff The main strategies to handle this intermittency include energy-storage, -transport, -diversity and -information The three first strategies smooth out the variability of production in time and space, whereas the last one aims a better balance between production and demand This study presents a literature review on the space-time variability of climate variables driving the intermittency of wind-, solar- and hydropower productions and their joint management in electricity systems A vast body of studies pertains to this question bringing results covering the full spectrum of resolutions and extents, using a variety of data sources, but mostly dealing with a single source Our synthesis highlights the consistency of these works, and, besides astronomic forcing, we identify three broad climatic regimes governing the variability of renewable production and load At sub-daily time scales, the three considered renewables have drastically different pattern sizes in response to small scale atmospheric processes At regional scales, large perturbation weather patterns consistently control wind and solar production, hydropower having a clearly distinct type of pattern At continental scales, all renewable sources and load seem to display patterns of constant space characteristics and no indication of marked temporal trends

Van der Waals Materials for Atomically-Thin Photovoltaics: Promise and Outlook

Abstract: Two-dimensional (2D) semiconductors provide a unique opportunity for optoelectronics due to their layered atomic structure, electronic and optical properties. To date, a majority of the application-oriented research in this field has been focused on field-effect electronics as well as photodetectors and light emitting diodes. Here we present a perspective on the use of 2D semiconductors for photovoltaic applications. We discuss photonic device designs that enable light trapping in nanometer-thickness absorber layers, and we also outline schemes for efficient carrier transport and collection. We further provide theoretical estimates of efficiency indicating that 2D semiconductors can indeed be competitive with and complementary to conventional photovoltaics, based on favorable energy bandgap, absorption, external radiative efficiency, along with recent experimental demonstrations. Photonic and electronic design of 2D semiconductor photovoltaics represents a new direction for realizing ultrathin, efficient solar cells with applications ranging from conventional power generation to portable and ultralight solar power.

Very short-term photovoltaic power forecasting with cloud modeling: A review

Abstract: This paper endeavors to provide the reader with an overview of the various tools needed to forecast photovoltaic (PV) power within a very short-term horizon. The study focuses on the specific application of a large scale grid-connected PV farm. Solar resource is largely underexploited worldwide whereas it exceeds by far humans’ energy needs. In the current context of global warming, PV energy could potentially play a major role to substitute fossil fuels within the main grid in the future. Indeed, the number of utility-scale PV farms is currently fast increasing globally, with planned capacities in excess of several hundred megawatts. This makes the cost of PV-generated electricity quickly plummet and reach parity with non-renewable resources. However, like many other renewable energy sources, PV power depends highly on weather conditions. This particularity makes PV energy difficult to dispatch unless a properly sized and controlled energy storage system (ESU) is used. An accurate power forecasting method is then required to ensure power continuity but also to manage the ramp rates of the overall power system. In order to perform these actions, the forecasting timeframe also called horizon must be first defined according to the grid operation that is considered. This leads to define both spatial and temporal resolutions. As a second step, an adequate source of input data must be selected. As a third step, the input data must be processed with statistical methods. Finally, the processed data are fed to a precise PV model. It is found that forecasting the irradiance and the cell temperature are the best approaches to forecast precisely swift PV power fluctuations due to the cloud cover. A combination of several sources of input data like satellite and land-based sky imaging also lead to the best results for very-short term forecasting.

Hybrid Concentrated Solar Thermal Power Systems: A Review

Abstract: Concentrated solar power (CSP), or solar thermal power, is an ideal technology to hybridize with other energy technologies for power generation. CSP shares technology with conventional power generation and can be readily integrated with other energy types into a synergistic system, which has many potential benefits including increased dispatchability and reliability, improved efficiency, reduced capital costs through equipment sharing, and the opportunity for flexible operation by alternating between energy sources, which can lead to improved overall efficiency through synergy of the different energy sources. Another advantage of CSP technology is the ability to readily store via thermal energy storage (TES), making the intermittent solar resource dispatchable. A review of CSP hybridization strategies with coal, natural gas, biofuels, geothermal, photovoltaic (PV), and wind is given. An overview of different configurations for hybridizing CSP with these other energy sources is also provided. Hybridized CSP plants present different types and levels of synergy, depending on the hybrid energy source, the location of the plant, the CSP technology used, and the plant configuration. Coal, natural gas, and biofuel hybrids with CSP present many opportunities to inject solar heat at various temperatures. These combustible fuels provide reliability, dispatchability, and flexibility but are not entirely renewable solutions (with the exception of biofuels). Geothermal, wind, and PV hybrid designs with CSP can be entirely renewable, but lack some of the benefits of hydrocarbon fuels. Effective geothermal-CSP hybrid designs require low temperature operation where efficiency is limited by the power cycle. Wind-CSP and PVT (photovoltaic/thermal) lack dispatchability, but have other advantages. The pursuit of ideal CSP hybrid systems is an important research topic as it allows for further development of CSP technologies while providing an immediate solution that increases the use of solar power.

Multistage Robust Unit Commitment With Dynamic Uncertainty Sets and Energy Storage

Abstract: The deep penetration of wind and solar power is a critical component of the future power grid. However, the intermittency and stochasticity of these renewable resources bring significant challenges to the reliable and economic operation of power systems. Motivated by these challenges, we present a multistage adaptive robust optimization model for the unit commitment (UC) problem, which models the sequential nature of the dispatch process and utilizes a new type of dynamic uncertainty sets to capture the temporal and spatial correlations of wind and solar power. The model also considers the operation of energy storage devices. We propose a simplified and effective affine policy for dispatch decisions, and develop an efficient algorithmic framework using a combination of constraint generation and duality-based reformulation with various improvements. Extensive computational experiments show that the proposed method can efficiently solve multistage robust UC problems on the Polish 2736-bus system under high dimensional uncertainty of 60 wind farms and 30 solar farms. The computational results also suggest that the proposed model leads to significant benefits in both costs and reliability over robust models with traditional uncertainty sets as well as deterministic models with reserve rules.

Hydro, wind and solar power as a base for a 100% renewable energy supply for South and Central America.

Abstract: Power systems for South and Central America based on 100% renewable energy (RE) in the year 2030 were calculated for the first time using an hourly resolved energy model. The region was subdivided into 15 sub-regions. Four different scenarios were considered: three according to different high voltage direct current (HVDC) transmission grid development levels (region, country, area-wide) and one integrated scenario that considers water desalination and industrial gas demand supplied by synthetic natural gas via power-to-gas (PtG). RE is not only able to cover 1813 TWh of estimated electricity demand of the area in 2030 but also able to generate the electricity needed to fulfil 3.9 billion m3 of water desalination and 640 TWhLHV of synthetic natural gas demand. Existing hydro dams can be used as virtual batteries for solar and wind electricity storage, diminishing the role of storage technologies. The results for total levelized cost of electricity (LCOE) are decreased from 62 €/MWh for a highly decentralized to 56 €/MWh for a highly centralized grid scenario (currency value of the year 2015). For the integrated scenario, the levelized cost of gas (LCOG) and the levelized cost of water (LCOW) are 95 €/MWhLHV and 0.91 €/m3, respectively. A reduction of 8% in total cost and 5% in electricity generation was achieved when integrating desalination and power-to-gas into the system.

Large heat pumps in Swedish district heating systems

Abstract: Power-to-heat solutions like heat pumps and electric boilers are foreseen to be possible future tools to stabilise international power markets with high proportions of variable power supply. Temporary low cost electricity can be used for heat generation at times with high availability of wind and solar power through substitution of ordinary heat supply, hence contributing to increased energy system sustainability. Power-to-heat installations in district heating systems are competitive due to low specific investment and installation costs for large electric boilers, heat pumps, and heat storages. Several large-scale heat pumps were installed in Swedish district heating systems during the 1980s, since a national electricity surplus from new nuclear power existed for some years. The aim of this paper is to summarise the accumulated operation experiences from these large Swedish heat pumps to support and facilitate planning of future power-to-heat solutions with heat pumps in district heating systems. Gained experiences consider; installed capacities, capacity utilisation, heat sources used, refrigerant replacements, refrigerant leakages, and wear of mechanical components. The major conclusion is that many of the large thirty-year-old heat pumps are still in operation, but with reduced capacity utilisation due to internal competition from waste and biomass cogeneration plants in the district heating systems.

Photovoltaic agriculture - New opportunity for photovoltaic applications in China

Abstract: Photovoltaic industry has been an important development direction of China's strategic emerging industries since 2012, and more and more attentions have been paid to broaden the domestic demand to solve the problem of overcapacity of China's PV industry. Photovoltaic agriculture, the combination of photovoltaic power generation and agricultural activities, is a natural response to supply the green and sustainable electricity for agriculture. There are several main application modes of photovoltaic agriculture such as photovoltaic agricultural greenhouse, photovoltaic breeding, photovoltaic wastewater purification, photovoltaic water pumping and new type rural solar power station. Photovoltaic agriculture can effectively alleviate the contradiction between more population and less land, powerfully promote the development of controlled environmental agriculture, evidently increase economic benefits of farmers, and significantly improve environment due to emissions reduction in China. In recent years, photovoltaic agriculture has a rapid development in China due to powerful support policies, flourishing controlled environmental agriculture, policy-oriented rural electrification and promising electric machinery for greenhouse. Therefore, photovoltaic agriculture provides new opportunity for China's photovoltaic industry, thus not only to solve the dilemma of overcapacity for China's photovoltaic industry effectively, but also to accelerate the development of modern agriculture in China. However, the more theoretical researches and practical exploration must be conducted to optimize the combination of photovoltaic power generation and agricultural planting. And the unified standards must be established to standardize the design and scale of projects of photovoltaic agriculture. Also, photovoltaic enterprises need to produce widely applicable photovoltaic products for agricultural production and farmers’ life.